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4. Anchors, whose symbolism is pretty clear, were thought to keep you steady - you also earned an anchor if you completed a voyage across the atlantic.

3. Most of them served as talismans, though. For instance - pigs and chickens were transported in wooden crates, and these crates floated, so they would often survive being washed overboard.

So, you'd get one tattooed on each foot, in order to share their luck.